Question

I have a web app that you can currently log into with either your email address or your username.

I’m developing an iPhone application and I’m just wondering if I should offer the ability to log in with your phone number. If this is the case, a user would first have to provide the service with a number on the web (an optional parameter).

I find it convenient on other services I use where I might not remember what email I have connected to it.

• Is this a good idea?
• Would you offer it in a service you were
  building?

I’m trying to decide if its worth the trouble to build.

NOTE: This number would strictly be used for authentication.

Answer 1

I think that if your service is not about phone numbers (calling, texting, etc., e.g., whatsapp, etc.) I would not add phone number authentication for a few reasons:

1. Some users might be deterred to provide a phone number due to privacy concerns (no matter how hard you try to explain them that you will keep it safe)
2. With the phone number you will now have 3 options to login with, which is way too much. You want to keep your mobile login screen very simple
3. Some people may think that they might get SMSs from you or get their phone bill charged somehow
4. Overloads your backend
5. Just keep it simple…:)

To add to that, I personally prefer just email, without a user name. So many sites require user names AND impose restrictions on how this user name should be structured, so you end up with tons of them. With emails, you can’t go so wrong – most people use a primary one to sign up for sites.

Hope that helps.